1. Field of the Invention
The present invention relates to an optical encoder that detects the position or the like of an object to be detected and its manufacturing method.
2. Description of the Related Art
Various types of optical encoders that detect the position of an object to be detected have been proposed.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2000-321018 (U.S. Pat. No. 6,410,911 B1) discloses an optical encoder including a sensor head having the following configuration. That is, the sensor head includes an LED chip serving as a light source, a scale having a grating pattern that transmits or reflects light emitted from the LED chip, and a light-sensitive chip serving as a photodetector that receives the light transmitted through or reflected by the scale. The light-sensitive chip and LED chip are mounted on a lead frame and are then integrally molded in transparent resin, thereby obtaining a small-sized and thin-type sensor head.
In an optical encoder, the scale having a grating pattern moves relatively to the above sensor head, thereby obtaining a displacement signal from the sensor head. The displacement signal is a two-phase analog signal having phases different by 90 degrees or a digital signal obtained by converting the above analog signal in a signal processing circuit, and periodically changes with the relative movement between the scale and sensor head.